Due to the constantly improved communication technology, various kinds of wireless communication devices, such as cell phones, have become an indispensable part in people's daily life. Moreover, since people in the modern society often travel for business or fun in different countries, it becomes very important the wireless communication devices is able to receive and transmit multi-band wireless electrical signals.
However, the wireless communication standards vary from area to area in the world. Currently, most of the available wireless communication device designs include a multi-band antenna or include multiple antennas of different frequency bands to receive and transmit wireless electrical signals of different frequency bands. However, there are difficulties in developing the multi-band antennas.
FIG. 1 is a block diagram of a tunable antenna device 1 which includes a switching circuit 15 to switch the connection of multiple antenna elements 13 to a first tunable matching circuit 11 or a second tunable matching circuit 12, in order to provide different frequency bands for receiving or transmitting multi-band wireless electrical signals.
According to the prior art tunable antenna device 1, multiple antenna elements 13 and multiple tunable matching circuits 11, 12 are required, and a switching circuit 15 is needed to switch the connection of the antenna elements 13 to one of the tunable matching circuits 11, 12 to achieve the multi-band tuning function. However, the multiple antenna elements 13, the multiple tunable matching circuits, i.e. the first and the second tunable matching circuit 11, 12, and the switching circuit 15 inevitably cause the problem of largely increased manufacturing cost.